1. Field of the Invention
This invention relates to slide fasteners of a concealed design and more particularly to a stringer of a warp-knit structure therefor.
2. Prior Art
Slide fasteners are well known which comprise a pair of rows of interlocking fastener elements formed from a continuous filament or wire and secured to respective folded edges of opposed stringer tapes, and such fasteners when closed by the slider conceal the elements from external view, only leaving a linear seam in the junction of the opposed tapes.
A prior art example of a warp-knit support tape for concealed-type slide fastener is disclosed in Japanese Laid-Open Utility Model Publication No. 51-44405, in which a particular wale adjacent to the path of a sewing needle is formed with fewer knit threads than the remaining portions of the type, more specifically with chain-forming threads omitted at that wale so as to reduce the height of this wale. This arrangement is intended to facilitate penetration of a sewing needle through an interwale groove between two adjacent wales, one higher or thicker than the other, bordering between a tape edge portion and a main web portion. However, due to these adjacent wales being different in knit structure and hence in elongation degree, the support tape when sewn is liable to pucker or other wise appear unsightly.
Another known warp-knit tape for use as a support for a concealed or masked type slide fastener is disclosed in Japanese Utility model Publication No. 54-35769 in which there is provided a particular thickened wale located at one tape edge and defined between adjacent interwale grooves which are wider than those in the remaining portions of the tape which are uniformly knitted. Such tape edge formation can be conveniently utilized for sewing a row of fastener elements thereon. However, since the tape web other than the tape edges is of a uniform knit structure, it is difficult to fold the tape on itself at the proper position for mounting the fastener elements, or to accurately define a location for sewing the tape onto a garment.
A further prior art warp-knit tape for slide fastener is described in Japanese Laid-Open Patent Publication No. 55-37241 in which the knit tape is comprised of chain stitches and open-lap stitches both of non-textured yarns combined to form longitudinally extending wales and laid-in weft threads formed with two different textured yarns. This tape is knitted uniformly throughout its width and suitable for use as a support tape for ordinary slide fasteners but lacks design considerations required for use as one for a concealed type of slide fastener.